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Re: [RFC] split floppy support off biosdisk

From: Javier Martín
Subject: Re: [RFC] split floppy support off biosdisk
Date: Tue, 17 Jun 2008 16:39:03 +0200

El mar, 17-06-2008 a las 11:06 +0800, Bean escribió:
> AFAIK, lzma decompresser don't need intermediate buffers, it operates
> directly on the input and output buffer, for example, the lzmadecoder
> in coreboot:
I think you didn't see the intermediate buffer because it is hidden in
the Probs field passed through the decoderstate struct. I've googled my
way through the net to find what the hell "probs" mean, and I still
don't understand ten contiguous lines of the LZMA code. What I could
find is that

provides the decoder with about 32KiB of "scratchpad" memory and will
reject decompressing files which "require" (as somehow indicated by the
first 5 bytes of the LZMA stream) more than that. I don't know if that
space is used for dictionaries, trees, forests or a Matrix full of
virtual monkeys hitting keys at random until the decompressed stream is
achieved, but its size seems to impose constraints at the time of
compression (probably a maximum -n level) that merit investigation.

PS: have you tested the performance of other compression algorithms like
gzip-deflate (much simpler) or bzip2 (near LZMA for small files but with
less memory requisites)?

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